Modified expansion law with Kodama-Hayward temperature for the horizon

TL;DR

This paper modifies Padmanabhan's horizon expansion law by incorporating the Kodama-Hayward temperature, extending it to various gravity theories, and expressing the law in terms of horizon surface energy and cosmic components.

Contribution

It introduces a modified expansion law using the Kodama-Hayward temperature applicable to multiple gravity theories, with a new formulation based on horizon surface energy.

Findings

Modified expansion law expressed with Kodama-Hayward temperature.

Extension of the law to higher order gravity theories.

Reformulation in terms of horizon surface energy and cosmic components.

Abstract

The expansion law proposed by Padmanabhan suggests that the evolution of the volume of the horizon is due to the difference between the degrees of freedom on the horizon and the degrees of freedom in the bulk enclosed by the horizon. In formulating this law, Padmanabhan used the temperature, $T=H/2\pi$, for a dynamical expansion. In this work, we modified the expansion law using Kodama-Hayward temperature, the dynamical temperature, for the horizon, first in (3+1) Einstein's gravity and extended it to higher order gravity theories such as (n+1) Einstein gravity, Gauss-Bonnet gravity, and more general Lovelock gravity. Contrary to the conventional approach, we expressed degrees of freedom of the horizon in terms of the surface energy of the horizon. Also, we have expressed modified expansion law in terms of cosmic components. It then turns out that it is possible to express the modified expansion law in a form as if $T=H/2\pi$ is the temperature of the dynamical horizon.